Radio receiving system



May 15, 1928. 1,670,149

C. W. HANSEN RADIO RECEIVING SYSTEM Filed Dec. 26, 1925 2 h ets-Sheet 1C. W. HANSEN RADIO RECEIVING SYSTEM May 15, 1928,

2 Sheets-Sheet 2 @rzbfbvz fl flzsaz Filed Dec. 26, 1925 Patented May 15,1928.

UNITED STATES.

PATENT, OFFICE.

CHRISTIAN W. HANSEN, OF CHICAGO, ILLINOIS, ASSIGNOR TO ZENITH RADIO COR-PORATION, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

RADIO RECEIVING SYSTEM.

Ap lication filed December as, 1925. Serial No. 77,859.

My invention relates to receiving sets employed in systems of radiocommunication that include thermionic valves and volume control devices,preferably rheostats in 011'- cuit between the heating filaments of thevalves and the source of filament heating current. One notespeciallyskilled in the use of radio receiving sets is apt to believe that hisset is turned off when the rheostat or other volume controlling elementis adjusted to cause the reception substantially to cease, yet withoutactually breaking the A battery circuit with the result that the batteryis often wasted.

My invention, in accordance with one of its characteristics, resides inthe provision of mechanism for automatically completing the throw of therheostat arm or other volume regulating element in case it is brought torest before fully reaching volume eifacing position.

In radio receiving systems, one rheostat is frequently made common tothe filaments of all of the radio frequency amplifying thermionic valvesof the set, the heating filament of the detector thermionic valve havinganother resistance, also in circuit with the same A battery, which isnot governed by the rheostat that pertains to the other valves. I,therefore, also desirably provide a switch through which the A batterysupplies its current to the filaments of all of the valves, this switchremaining closed throughout the normally effective range of operation ofthe rheostat and being opened when the rheostat is adjusted tosubstantially efl'ace the reception. The switch is of particular servicein disconnecting the filament of the detector valve and also supplementsthe function of the automatic device for discontinuing the flow ofcurrent from the A. battery through the heating filaments of theamplifying valves as well, an advantageous feature in the event that therheostat arm happens to remain in engagement with the rheostatresistance.

I will explain my invention more fully by reference to the accompanyingdrawings in which Fig. 1 is a diagrammatic View of one receiving systemequipped in accordance with the preferred embodiment of the invention;Fig. 2 is a front view of the preferred form of rheostat and automaticdevice for positively opening the. circuit of the A battery; Fig. 3 is asectional View on line 33 of Fig. 2; Fig. 4 is a sectional view on line44 of Fig. 2; and Fig. 5 is a persp'ec:

tive view illustrating the rheostat arm and tennae and not with shortantennae, and the grounded primary coupler transformer winding 3. Thestationary secondary winding 4: of the vario coupler is in series with arotatively adjustable winding 5. The variable secondary tuning condenser6 is in shunt relation to the coils 1 and 5, taken together, being thusalso traversed by radio frequency current. The elements 4, 5 and 6 arethus in a resonant circuit whose terminals are connected with the inputelectrode or grid 7 and the heatin filament 8 of a. radio frequencyamplifying thermionic valve 9. Said valve also includes the output plateor electrode 10. The output circuit which includes this electrode alsocontains a stationary primary radio frequency transformer winding 11, arotatively adjustable windin 12 in series with the winding 11, and thebattery 13 in series with. both windings 11 and 12. The stationary radiofrequency transformer secondary winding 14 is in inductive relation tothe windings 11 and 12. The secondary 14 is shunted by a variablesecondary tuning condenser 15.

There is thus a second resonant circuit in cascade relation to the firstand whose terminals are connected with the input electrode ,or grid 16and the heating filament 17 of a radio frequency amplifying thermionicvalve 18. Said valve 18 also includes the winding 20, and the aforesaidB battery.

The stationary radio frequency transformer secondary winding 22 is ininductive relation to the windings 20 and 21. The secondary 22 isshunted by a variable secondary tuning condenser 23. i There is thus athird resonant circuit in cascade relation to the other two and whoseterminals are connected with the input electrode or grid 24 and theheating filament 25 of a radlo frequency amplifying thermionic valve26.' Saidfvalve 26 also includes the output plate or electrode 27. Theoutput circuit which includes this electrode 27 also contains astationary primary radio frequency transformer winding 28, a rotatively.

adjustable winding 29 'in series. with the winding 28, and the B battery13. The stationary radio. frequency transformer secondary winding 30 isin inductive relation to the'windings 28 and 29. The secondary 30 isshunted by a variable secondary tuning condenser 31. i

There is thus a fourth resonant circuit in cascade relation tothe otherthree and whose terminals are connected with the input electrode or grid32 and the heating filament 33 ofa thermionic detector valve, 34, thisresonant circuit being-connected with the grid 32 by way of the usualcondenser 35 and the high resistance leakage path 36 in shunt to thiscondenser. Said valve 34 also includes the output plate or electrode 37.The output circuit which includes this elect-rode 37 supplies thetelephone receiver 38 with audio frequency current, the output circuitcontaining the electrode 37 and receiver 38 also containing a portion ofthe B battery. The telephone receiver is shunted by th usual by-passcondenser 39. p

I have shown a cascade of four radio frequency tuning circuits but theinvention may be practiced with one radio frequency tuning circuit. Allof the adjustable elements, hitherto described, of the receivingcircuit, may, if desired, be simultaneously regulated by unitaryadjusting means in accordance with well-known practice.

The heating filaments of the, radio frequency amplifying thermionicvalves 9, 18 and 26 and the heating filament of the detector thermionicvalve 34 are supplied with heating current from the A battery 40, orother source of current. The filaments of the valves 9, 18 and 26 aresupplied through the rheostat resistance 41. The filament of the valve34 is supplied through the resistance 42. One extremity of the rheostatresistance 41 is permanently connected with the filaments to which itpertains. The contacting switch arm 43 of the rheostat sweeps over theresistance 41 between the connected extremity of the resistance and thefree or unconnected extremity of the resistance in effecting thefilament adjustment, a stop 44 being generally employed to retain aminimum amount of the resistance 41 in circuit when the receiving set isfunctioning. When the rheostat arm 43 is swung to the anism is inclusiveof a disc45 that is fixed with respect to the shaft 46 that carries therheostat arm, this shaft being journaled in a bearing 4( which iscarried by the support 48 for the rheostat resistance. Theshaft isprovided with the usual operating knob or handle 49. The disc 45 ismechanically coupled with thearm 43 by.virtue of the shaft 46 passingthrough the arm and disc and the tail 50 upon the arm that passes into Yan opening 51 in the disc. This disc isconstituted a cam disc by beingprovided with a peripheral notch 52. A spring 53 is anchoreo. at one endupon the resistance support 48 and has a kinked portion 54. Thespring'is so located that the kink 54 therein Wlll enter the notch 52when the rheostat arm is in engagement with the concludingportion of thelow volume extremity of the rheostat resistance, the spring thenfunctioning to complete the resistance excluding motion of the rheostatarm preferably to an extent which will disengage the rheostat armfromthe resistance, though the invention need not be thus limited as willpresently appear. The spring 53, in addition to performing itsmechanical function, desirably alsoconstitutes a contacting member of aswitch in which vevent is is provided with a contacting point 55 at itsfree end. The contact 56, which is complemental to the contact-55, isdesirably provided upon the free end of another spring 57 which is alsocarried by the resistance support 48. When the rheostat arm is in theportion of its range of movement in which the filament current isadjustable thereby, the unnotched portion of the disc engages the kinkedportion 54 of the spring 53 to maintain the contacts 55 and 56 inengagement, the circuit of the A battery serially including thesecontacts that are thus traversed by the A battery current flowing to thefilaments of all of the valves. When the rheostat is out of circuit andthe kinked portion 54 of the spring 53 consequently enters the notch 52,the contact 55 is witharm 43 has not been moved entirely out ofconnection with the resistance 41.

Changes may be made without departing from the invention.

Having thus described my invention, I claim:

1. A radio receiving system including a radio frequency amplifyingthermionic valve having input and output electrodes and a heatingelement in a heating circuit; a thermionic detector valve also havinginput and output electrodes and a heating element in a heating circuit;a source of current for inclusion in circuit with each of said heatingelements; a rheostat including a resistance and a switch arm connectiblewith different portions of the resistance to vary the amount thereofthat is included in circuit, said switch arm and the portion of theresistance selected thereby being serially in the heating circuit ofsaid radio frequency amplifying valve; and means controlled by saidswitch arm for opening said heating circuits and rendered operative bysaid switch arm when said arm is near the free extremity of saidresistance.

2. A radio receiving system including a radio frequency amplifyingthermionic valve having input and output electrodes and a heatingelement in a heating circuit; a thermionic detector valve also havinginput and output electrodes and a heating element in a heating circuit;a source of current for inclusion in circuit with each of said heatingelements; a rheostat including a resistance and a switch arm connectiblewith different portions of the resistance to vary the amount thereofthat is included in circuit, said switch arm and the portion of theresistance selected thereby being serially in the heating circuit ofsaid radio frequency amplifying valve, the heating circuit of thedetector valve being independent of the heatingcircuit of the radiofrequency amplifying valve; a switch in the heating circuit of thedetector valve; and means controlled by said switch arm for completingthe circuit opening movement thereof and for opening the switch in theheating circuit of the detector valve and rendered operative by. saidswitch arm when said arm is near the free extremity of said resistance.

In witness whereof, I hereunto subscribe my name.

- CHRISTIAN W. HANSEN.

